Independent suspension for multi-use vehicle

ABSTRACT

A half-track vehicle includes a frame, first and second beams having forward and rearward wheels attached thereto, and first and second suspension systems. The frame includes a first side and a second side, and the first suspension system suspends the first beam from the frame adjacent the first side of the frame and the second suspension system suspends the second beam from the frame adjacent the second side of the frame. Each suspension system includes at least one element, such as a trailing arm, and A-arm, and a transverse suspension member, that is attached to one of frame and an associated one of the first and second beams in a manner that permits three degrees of rotational movement and that transmits motive force from the first and second beams to the frame.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to vehicle suspension systemsand, more particularly, toward an independently suspended beam structurefor a multi-use vehicle.

2. Description of Related Art

It is known to independently suspend wheels from a vehicle frame. Anindependently suspended wheel is able to move in one or more directionswithout affecting the movement of any other wheels. It is desirable toindependently suspend wheels to improve the ride of a vehicle whentraveling over uneven ground. It is also desirable to use a track oneach side of the vehicle. The use of a track, rather than individualwheels only, improves the vehicle's flotation on soft ground as well asthe traction. It is particularly important to use an independentsuspension system when a track is used, to maximize the amount ofsurface area of each track in contact with the ground on each side ofthe vehicle.

It is also known to suspend beams from vehicles. In a typicalconfiguration, a beam is suspended on each side of a vehicle. Two ormore wheels are attached to the beam. Typically, axles or otherstructures rigidly interconnect the beams so that the beams movetogether relative to the frame. These types of structures are normallyused in areas where the terrain is likely to be substantially level.

Some suspension systems are like those used on military vehicles and areschematically illustrated in FIG. 1. This half-track structure 10includes a track 12 that surrounds a plurality of wheels 14, 16. The twoend wheels 14 are mounted directly to the frame with no suspensionsystem. The main load-bearing wheels 16 are individually suspended fromthe frame.

Other suspension systems are used on vehicles similar to the SNO CATvehicle, which is made by Tucker Sno Cat Corporation of Oregon, andschematically illustrated in FIG. 2. This half-track structure 20includes a track 22 surrounding a plurality of wheels 24, 26. The topwheel 24 is connected to a central axle 28. The central axle 28 providesthe drive function and is suspended from the vehicle. The remainingwheels 26 are attached to the central axle 28. The track 22 can rotateabout the central axle 28, but the central axle links the motion of thetwo structures 20 on either side of the vehicle.

Finally, there are MUV suspension systems, such as is schematicallyillustrated in FIG. 3. In this structure 30, a trailing arm 32 isattached to each beam 34 (only one beam shown in the drawing) andconnects the beam to a frame (not shown). While each beam may includeits own springs or cushions 36, the axles 38 conventionally extendacross the vehicle, thereby linking the motion of the two beams.

Such structures are unsatisfactory for use in an off-road setting.Typically, an MUV is used in an area where there are substantialdifferences in terrain on both sides of the vehicle. It is alsodesirable to use a half-track on an MUV to permit the MUV to traversemany types of terrain, particularly in wet areas, without sinking.However, no structure has been developed that permits each beam to beindependently suspended. In an off-road setting, an independentsuspension would be particularly desirable since the variations in thelevel of the ground can be substantial.

Further, one of the problems to be solved with off-road vehicles is thatof travel over large objects, such as logs. Manufacturers have addressedthis problem by using low pressure tires. The use of a low pressure tireallows the tire to deform when it encounters an object. This increasesthe surface area, and hence the friction, between the low pressure tireand the object, enabling the motive force of the vehicle to push thevehicle up and over the object. However, the use of low pressure tiresis not desirable for use with a tracked vehicle. If a low pressure tireis used and the tire deforms, the track tends to have an increasedamount of slack at the time of deformation, substantially increasing therisk of the track slipping off the tires.

Moreover, if a tracked vehicle is to be used, a high pressure tireshould be used to prevent the detachment of the track. Unfortunately,the use of such a tire creates a reduced amount of surface area contactbetween the vehicle and the obstacle, which causes the track to slipagainst the obstacle and prevents the vehicle from passing over theobstacle. Therefore, in the prior art a high pressure tire is known tobe undesirable.

SUMMARY OF THE INVENTION

The present invention is directed toward an improved suspension systemfor an off road or multi-use vehicle. More specifically, the presentinvention is directed toward a half-track vehicle incorporating asuspension system that is adapted for use over rough terrain.

In accordance with the present invention, a half-track vehicle includesa frame, first and second beams having forward and rearward wheelsattached thereto, and first and second suspension systems. The frameincludes a first side and a second side, and the first suspension systemsuspends the first beam from the frame adjacent the first side of theframe and the second suspension system suspends the second beam from theframe adjacent the second side of the frame. Each suspension systemincludes at least one element that is attached to one of the frame andan associated one of the first and second beams in a manner that permitsthree degrees of rotational movement and that transmits motive forcefrom the first and second beams to the frame.

In further accordance with the present invention, each of the suspensionsystems includes a trailing arm that is secured between the beam and theframe. The trailing arm is preferably attached to a top of the beam atforward end thereof adjacent the forward wheel, and extends forwardlytherefrom to the frame.

In further accordance with the present invention, the suspension systemsinclude an A-arm that is secured between the associated beam and theframe. The A-arm is preferably secured to a top of the beam at forwardend of the beam adjacent the forward wheel.

In further accordance with the present invention, the suspension systemsinclude transverse suspension members that extend from a proximal endsecured to the beams to a distal end disposed at least adjacent thelongitudinal centerline of the vehicle. In accordance with one versionof the invention, the vehicle frame includes a support structuredisposed along the longitudinal centerline to which the transversesuspension member distal ends are rotatably secured. In accordance withanother version of the invention, the proximal ends of the transversesuspension members are secured to an associated beam on one side of thevehicle and the distal ends of the transverse suspension members aresecured to the frame on the opposite side of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the invention will be apparent withreference to the following description and drawings, wherein:

FIG. 1 is a schematic side view of a first prior art half-tracksuspension structure;

FIG. 2 is a schematic side view of a second prior art half-tracksuspension structure;

FIG. 3 is a schematic side view of a third prior art half-tracksuspension structure;

FIG. 4 is a schematic side view of an embodiment of a half-tracksuspension structure and vehicle in accordance with the presentinvention;

FIG. 5 is a schematic end view of the vehicle shown in FIG. 4;

FIG. 6 is a perspective view, partially cut away, of a modifiedembodiment of a half-track suspension structure;

FIGS. 7 a–7 b schematically illustrate a vehicle with aforwardly/rearwardly disposed trailing arm traversing an obstacle;

FIG. 8 is a perspective view of a further modified embodiment of ahalf-track suspension structure;

FIGS. 9 a–9 e schematically illustrate several transverse suspensionmember attachment schemes according to the present invention;

FIGS. 10 a–10 b schematically illustrate the effect of differences inlength of the suspension members;

FIG. 11 is a partial perspective view of a further modified embodimentof a half track suspension structure including an A-arm;

FIG. 12 is a schematic view of a modified attachment for an A-armsuspension system;

FIG. 13 schematically illustrates a further modified attachment for anA-arm suspension system;

FIG. 14 schematically illustrates a comparison of the motion of the midaxle 204 along a vertical path V, a rotational path R, and a desirablemechanical compliance angle M;

FIG. 15 schematically illustrates wheel camber; and,

FIG. 16 schematically illustrates wheel toe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a suspension system for a half-trackvehicle. Initially, it is noted that the drawings are not to scale, butwill be more easily understood by a person of ordinary skill in the artthan drawings from another perspective or drawings shown in properproportion. It is further noted that the drawings do not show any otherstructures attached to the vehicle, nor do they show any structuresnecessary for the functioning of the vehicle that are not directlyrelated to the suspension structure disclosed. Accordingly, the vehicleshown in the drawing figures may not be functional without the otherparts, such as a drive train and the like. However, any drive train thatmay be used in connection with the present structure is relativelyconventional in nature. A person of ordinary skill in the art can easilyadapt a known MUV or ATV drive train for use in connection with thepresent vehicle.

It is also noted that the present structure is also capable of beingused on a trailer that has no independent motive power. The use of astructure on a trailer is useful in such areas as in agriculturalapplications. In such applications, it is important to minimize thepressure on the ground from the trailer, to prevent damaging crops orother plants. Another area in which a trailer would be useful occurswhen the trailer is to be used on snow or in a muddy area, particularlyif there is rough terrain. In these cases and similar situations, theuse of a tracked vehicle distributes the weight of the trailer,minimizing the weight in any one particular area. In such a situation,the independent suspension to be described below remains important, dueto the inherent unevenness of the terrain. However, no motive power needbe used, since a tow vehicle pulls the trailer. Accordingly, there is noabsolute necessity for a drive train assembly to be used in connectionwith the present vehicle in such a situation.

FIGS. 4 and 5 schematically illustrate a rear portion of a half-trackvehicle according to first embodiment of the present invention. Thehalf-track vehicle 102 includes a frame 104, a pair of tracks 106, firstand second beams 108, 110, a plurality of wheels 112 a, 112 b, 113 a,113 b, a plurality of cushions 124, and first and second trailing arms128, 130. The vehicle further includes front wheels (not shown in FIGS.4–5). The wheels are associated with one of a first and second lateralside 116, 118 of the vehicle 102 and are referred to hereinafter asbeing either a mid wheel 112 a, 113 a or a rear wheel 112 b, 113 b,respectively. Preferably, the rear wheels 112 b, 113 b are powered byknown drive means (not shown), as will be apparent from the followingdiscussion. Alternatively, the mid wheels 112 a, 113 a, or both the midand rear wheels may be powered.

Each of the wheels 112 a, 112 b on the first lateral side 116 of theframe 104 is connected to the first beam 108, while each of the wheels113 a, 113 b on the second or opposite lateral side 118 of the frame 104is connected to a second beam 110. An axle 114 is associated with eachof the wheels. The axles 114 are secured to the beams 108, 110 andextend outwardly therefrom, with the associated wheel being secured toan end of the axle, as is well known in the art. Naturally, if the rearwheels are powered, the rear axles will extend inwardly from the beamfor connection to the drive means (not shown). Each of the axles 114 inthe illustrated embodiment extend only between one of the beams 108, 110and the associated wheel 112 a, 112 b, 113 a, 113 b such that no singleaxle interconnects wheels on the first and second sides 116, 118 of thevehicle.

Each beam 108, 110 is preferably made from two parts 134, 136 thatslidably interfit with one another. In order to place the wheels withinthe track, the wheels 112 a, 112 b, 113 a, 113 b are attached to theaxles 114, which are each secured to one of the beam parts 134, 136, andthe two beam parts 134, 136 are slidably interfit with one another. Thetrack 106 is then placed around the wheels, and the two parts 134, 136are slid away from each other until the track 106 has the desiredtension. Thereafter, the two beam parts 134, 136 are attached to oneanother using conventional techniques, such as mechanical fasteners.

Because it is often desirable to make the beams of steel for strengthand durability, the two beam parts 134, 136 may be joined by welding,and an additional track-tensioning device (i.e., one associated withjust one of the beam portions 134, 136) may be used to adjust the tracktension which varies over time, due to age, use, humidity, and the like.Therefore, although the sliding feature and joining techniques describedhereinbefore are illustrative of the preferred embodiment, the presentinvention is not limited thereto. Rather, it is believed apparent thatmany other structures and methods may be used to properly position andtension the track 106 on the wheels. In addition, while the use of thetrack 106 is desirable, it is not necessary, and the independentlysuspended beam structure can be used only with the wheels should thetrack be omitted.

A suspension system connects the beams 108, 110 to the frame 104 andpermits the beams on each side of the frame to move relative to theframe and substantially independently of one another. The suspensionsystem includes the cushions 124 and the trailing arms 128, 130.

With continuing reference to FIGS. 4 and 5, one of the cushions 124extends between the first beam 108 and the frame 104, while an identicalcushion 124 extends between the second beam 110 and the frame 104.Alternatively, a pair of cushions could be used on each side 116, 118,wherein one of the cushions will be disposed adjacent the mid wheel 112a, 113 a, while another of the cushions will be disposed adjacent therear wheels 112 b, 113 b. The cushions 124 shown in FIGS. 4–5 act assprings that resist compression and tension, and thus serve to dampenvertical movement of the frame and beams relative to one another.Naturally, any known cushioning mechanism can be used, such as a shockabsorber, hydraulic system, or the like, depending on the level ofstrength and durability needed. A person of ordinary skill in the art isable to select an appropriate structure for cushioning the movement ofany particular beam structure.

The first trailing arm 128 is on the first side 116 of the vehicle andextends between the first beam 108 and the frame 104. The secondtrailing arm 130 is on the second side 118 of the vehicle and extendsbetween the second beam 110 and the frame 104. More specifically, thetrailing arms 128, 130 include a first end 128 a, 130 a pivotallysecured to the associated beam 108, 110, respectively, and a second end128 b, 130 b pivotally secured to the frame 104.

The pivotal connection between the trailing arm first end 128 a, 130 aand the beam 108, 110, on one hand, and between the trailing arm secondend 128 b, 130 b and the frame 104, on the other hand, preferably is aswivel-type ball-and-socket type connection that permits the up, down,left and right motion of the trailing arm relative to the beam andframe. While most of the rotary motion at the connections will be invertical direction as the beam 108, 110 moves upward and downwardrelative to the frame 104, a certain degree of horizontal pivoting, or acertain degree of movement including a horizontal component, may bedesirable should the beams twist or cant during use. In addition topermitting a certain range of motion between the frame 104 and the beams108, 110, the trailing arms 128, 130 also serve as the primary paths fortransmitting driving force from the track structure to the frame 104,and therefore are relatively rigid. Accordingly, the trailing arm 128,130 and the trailing arm joints or connections must be sufficientlystrong to bear the forces communicated therethrough.

Because each of the first and second beams 108, 110 is separately joinedto the frame 104 and is not joined to the other of the first and secondbeams 108, 110, the first and second beams are permitted to moveindependently of each other. Thus, one of the beams 108, 110 mayraise/dip and rebound without causing the frame to twist due to theother beam 110, 108 simultaneously dipping/raising and rebounding.

It is noted herein that the illustration of the present invention inFIGS. 4 and 5 is somewhat schematic and should not be taken tooliterally. For example, in the drawings the beams 108, 110 arepositioned entirely below the frame 104. This depiction is for ease ofunderstanding. The beams 108, 110 can be positioned nearer to andpartially overlapping the frame 104. In addition, the frame 104 is shownas being generally rectangular with a square cross section. The frame104 need not have such a geometric shape. In addition, the frame 104 mayinclude any number of crossbars, rather than or in addition to the endcross bars shown. The cushions 124 and the trailing arms 128, 130 areshown as being attached near the bottom of the frame 104. However, thecushions 124 and the trailing arms 128, 130 need not be so positioned,but may instead be attached to the frame 104 at any convenient location.

Turning now to FIGS. 6–16, a rear portion of a half-track vehicleincorporating a different configurations of a suspension systemaccording to the present invention are illustrated, it being noted thatthe vehicle frame has not been shown in the drawing for purposes ofclarity. Moreover, insofar as the structure on each lateral side of thehalf-track vehicle is identical, the following description is directedtoward only one side, where appropriate, for purposes of brevity.Further, insofar as several of the following configurations have partsin common, identical reference numbers are used in the followingfigures, where appropriate.

FIG. 6 is a partial cut away view of the suspension system 200 of thepresent invention. The suspension system 200 includes a beam 202 havinga forward end 202 a and a rearward end 202 b. A forward or mid axle 204a and associated mid hub 206 a are secured to the forward end 202 a ofthe beam while a rear axle 204 b and associated rear hub 206 b aresecured to the rearward end 202 b of the beam 202. A mid wheel 208 a issecured to the mid hub 206 a and a rear wheel 208 b is secured to therear hub 206 b. A track 210 is stretched around the outside of thewheels 208 a, 208 b.

The track 210 is preferably made of rubber and is most preferably aboutan inch thick. The wheels 208 a, 208 b are preferably made of arelatively hard material and the beam 202 is adjusted properly to fitthe track 210. The appropriate adjustment and hardness prevents thetrack 210 from slipping off the wheels 208 a, 208 b due to the wheels208 compressing to too great an extent. The beam 202 is preferably madeof two parts 212, 214 that slidingly interfit one another, as discussedpreviously with regard to the embodiment of FIGS. 4–5. A drive shaft 215is attached to the rear hub 206 b to provide motive power to the rearwheels 208 b. Alternatively, the drive shaft 215 may be attached to themid hub 206 a. Further, a drive mechanism to transfer motive powerbetween the wheels 208 a, 208 b, such as a drive chain, may also beemployed.

The beam 202 is suspended from the frame (not shown) by a trailing arm216, three transverse suspension members 218 a, 218 b, 218 c, and firstand second cushions 220 a, 220 b. The trailing arm 216, transversesuspension members 218 a, 218 b, 218 c, and cushions 220 a, 220 b areattached, either directly or indirectly, to both the beam 202 and theframe. Further, the trailing arm 216, transverse suspension members 218a, 218 b, 218 c, and cushions 220 a, 220 b are attached to the beamand/or the frame via a joint or series of joints that permit motion withthree degrees of rotational freedom, such as a ball joint typeconnection or rubber bushings. It will be apparent to a person ofordinary skill in the art that the end that is attached to the framemust also permit rotation about a primary axis of rotation, with somedegree of freedom about other axes in order to be functional.

The trailing arm 216 has a first or forward end 216 a attached to theframe and a second or rearward end 216 b attached to a top 224 of thebeam 202 at the forward end 202 a thereof. The position of the trailingarm 216 is important to force the mid axle 204 a at the forward end 202a of the beam 202 to retract at a predetermined mechanical complianceangle. Preferably, the mechanical compliance angle is between about 5°and 15°. Because the mid axle 204 a does not extend across the width ofthe vehicle (i.e., is not attached to the opposite beam), when the midwheel engages or rides over an obstacle, the beam 202 tends to rotateabout the rear hub 206 a, as it is the most secure, being attached tothe drive shaft 215. In an ordinary rotation, the mid axle 204 a wouldtend to move primarily upwardly, and then would move at an anglebackwardly. However, in order to have an appropriate ride, it isdesirable for the mid axle 204 a to move more angularly at themechanical compliance angle. The use of the trailing arm 216 in theillustrated relatively forward position provides a relatively stiffguidance system for the forward end 202 a of the beam, causing the midaxle 204 a to move more rearwardly as it deflects upwardly uponengagement with rocks, sticks, ruts, and other objects that areencountered in an off-road environment.

FIGS. 7 a–7 b illustrate the difference in movement of the beam 202 whenthe trailing arm 216 is positioned at the forward end 202 a and therearward end 202 b of the beam 202. These drawings show only the beam202, wheels 208 a, 208 b, trailing arm 216, and frame 226 in a schematicview, rather than the detailed structure of FIG. 6.

FIG. 7 a illustrates the motion of the mid wheel 208 a upon encounteringan obstacle 228 when the trailing arm 216 is attached to the rearwardend 202 b of the beam 202. Because the trailing arm 216 is attached tothe rearward end 202 b of the beam 202, when the mid wheel 208 aencounters the obstacle 228, the mid wheel 208 a will tend to moveindependently of the motion of the trailing arm 216, and will tend torotate around the axis of the rear wheel 208 b. Because the beam 202 isrelatively long, the motion of the mid wheel 208 a will be mainlydirected upwardly, as shown by the arrow in FIG. 7 a. Although themotion is rotational, the length of the beam 202 does not provide asubstantial angular deviation from vertical until the mid wheel 208 ahas reached some distance from the ground. Only when the rear wheel 208b contacts the obstacle 228 will the trailing arm 216 have a substantialeffect to cause the beam 202 to retract rearwardly in addition toupwardly.

FIG. 7 b illustrates the motion of the mid wheel 208 a upon encounteringan obstacle 228 when the trailing arm 216 is attached to the forward end202 a of the beam 202. Because the trailing arm 216 is attached to theforward end 202 a of the beam 202, the mid wheel 208 a will rotateupwardly about the point that the trailing arm 216 attaches to the frame226. This is because the length of the trailing arm 216 is relativelyshort as compared to the length of the beam 202, and because thetrailing arm 216 is attached near the attachment point of the mid wheel208 a. Because of the different rotation axis, the motion of the midwheel 208 a will tend to have a substantially greater rearwardcomponent, i.e., toward the direction of the rearward end 202 b of thebeam 202, than in the case shown in FIG. 7 a. The rotational movement ofthe mid wheel 208 a in the upward and rearward directions is shown bythe arrow in FIG. 7( b).

It is most desirable that the mid wheel 208 a moves in a manner similarto that shown in FIG. 7 b. When the mid wheel 208 a moves rearwardly atthe desired mechanical compliance angle of between about 5° and about15°, the shock load to the vehicle is reduced and thereby improves theride for the passenger.

A forward cushion 220 a and a rearward cushion 220 b are used in thepresent embodiment, as illustrated in FIG. 6. The forward cushion 220 ais preferably placed near the forward end 202 a of the beam while therearward cushion is preferably placed near the rearward end 202 b of thebeam 202. However, the forward and rearward cushions 220 a, 220 b can beplaced in other locations either directly or indirectly attached to thebeam 202. The cushions 220 a, 220 b primarily serve to enhance the rideof the vehicle, but may also serve as a stop to prevent over rotation ofthe beam 202. Alternatively, a stop (not shown) can be incorporated intothe trailing arm 216 to limit rotation of the trailing arm 216.

With reference to FIG. 8, a modified version of the embodiment describedhereinbefore with regard to FIGS. 6–7 b is illustrated. Insofar as manyparts of the vehicle shown in FIG. 8 are identical to those describedwith regard to FIG. 6, those parts are given the same reference numbersin FIG. 8, and are not further described hereinafter.

The embodiment of FIG. 8 includes a stabilizer bar 230 that extendsacross the width of the vehicle and interconnecting the beams 202 onfirst and second sides of the vehicle. The stabilizer bar is secured ateach end 230 a, 230 b to one of the beams 202, and is rotatably securedat a mid-section 230 c to the frame (not shown). In use, the stabilizerbar 230 generally serves to equalize the vertically-oriented forcesexperienced by the beams 202. If further information regarding thestabilizer bar 230 is desired, reference should be made to applicant'sco-pending application Ser. No. 10/382,384, filed Mar. 6, 2003.

FIGS. 9 a–9 e illustrate a series of preferred embodiments for attachingthe transverse suspension members 218 a, 218 b, 218 of FIGS. 6 and 8 tothe frame, with the view being generally from the end of the vehicle.Each of FIGS. 9 a through 9 e shows the beams 202, mid axles 204 a, midwheels 208 a, and one transverse suspension member 218 a extending froma respective beam 202. Also shown in each drawing is at least a portionof two or more frame portions 250, 252.

In this regard it is noted that a conventional all terrain vehicle frameis generally formed as a series of linked components. The same is trueof the frame of the MUV in the present case. The frame portions 250,252, while not shown as being linked to one another in these drawingfigures, are at least indirectly linked to one another throughadditional frame portions (not shown). The frame of an ATV typicallyincludes at least one frame rail 250 that is offset from a centerline ofthe vehicle so as to extend along the vehicle relatively closer to oneof the beams 202. Linking or cross members (not shown) extend betweenthe frame rails 250. In the present case, the frame includes anadditional support 252, which serves as a center beam extending alongthe centerline of the vehicle. The additional support is secured to oneof the cross members or another frame element (not shown). Each of thedrawings shows only one transverse suspension member 218 a for ease ofexplanation and illustration. It will be understood by a person ofordinary skill in the art that the other transverse suspension members218 b, 218 c are configured and attached in a similar manner.

FIGS. 9 a and 9 b illustrate one preferred manner of attaching thetransverse suspension member 218 a to the frame 250, 252. With referenceto FIG. 9 b, each of the transverse suspension members 218 a areattached at a first end 218 a′ to one beam 202. The second end 218 a″ ofthe transverse suspension members 218 a are attached to the supportstructure 252 that is disposed at or adjacent the longitudinalcenterline 258 of the vehicle.

With reference to FIG. 9 a, the second ends 218 a″ integrally include atubular housing 254 defining a passageway that is oriented generallytransverse (i.e., perpendicular) to the longitudinal axis or length ofthe transverse suspension members. The tubular housings 254 are placednext to one another such that the passageways defined thereby are inalignment with one another and the centerline so as to permit theinsertion of a shaft or fastener 256, such as a pin or bolt,therethrough. The shaft or fastener 256 serves as a hinge pin over whichthe tubular housings 254, and hence the transverse suspension members218 a, pivot or rotate. The pin or fastener 256 is secured to a portionof the vehicle body or frame 250 through the support structure 252, andpreferably held in place by a stop 262, such as a locking nut, cotterpin, locking clip, weld, etc. In the illustrated embodiment, the supportstructure 252 is a plate or bracket extending downwardly from the frameor body that includes a pair of aligned holes through which the pin orfastener 256 extends, so that the tubular housings are receivedpartially within the support structure. The precise configuration of thefastener 256, stops 262, and support structure 252 is unimportant,except that the tubular housings 254 provided at the second ends 218 a″of the transverse suspension members 218 a must be able to rotategenerally along one axis and must be secured to the frame or body of thevehicle. Any equivalent or interchangeable structure known to a personof ordinary skill in the art may be substituted for that shown hereinwithout departing from the scope and spirit of the present invention.

FIGS. 9 c and 9 d illustrate a second manner of securing the transversesuspension members 218 a, 218 b, 218 c to the frame is illustrated.Insofar as many components of the assembly shown in FIGS. 9 c–9 d areidentical to those of FIGS. 9 a–9 b, such components are given identicalreference numbers and are not described in detail hereinafter. In FIGS.9 c–9 d the support structure 252 is a pair of plates or bracketsextending downwardly from the frame or body, each of which includesfirst and second holes through which one of the pins or fasteners 256extends. The pair of plates or brackets are spaced apart a distance anddimensioned such that the tubular housings are received therebetween andlaterally offset from one another. One of the tubular housings isdisposed within the support structure 252 such that the passagewayprovided thereby is aligned with the first holes formed in the plates orbrackets so as to permit the pin or fastener 256 to extend through thefirst holes and the tubular housing. Similarly, the other tubularhousing is disposed within the support structure 252 such that thepassageway provided thereby is aligned with the second holes formed inthe plates or brackets so as to permit another pin or fastener 256 toextend through the second holes and the tubular housing. The preciseconfiguration of the pins or fasteners 256, stops 262, and supportstructure 252 is unimportant, except that the second ends 218 a″ of thetransverse suspension members 218 a must be able to rotate generallyalong one axis and must be secured to the frame or body of the vehicle.

FIG. 9 e illustrates a further manner of connecting the transversesuspension members 218 a, 218 b, 218 c to the frame in accordance withthe present invention. Each transverse suspension member 218 a isattached at a first end 218 a′ to one beam 202. Each transversesuspension member 218 extends to a second end 218 a″ that is locatedadjacent the frame portion 250 on the opposite side of the longitudinalcenterline 258 of the vehicle from the respective first end of thetransverse suspension member 218. The details of the attachmentstructure are not shown, but may be substantially similar to those shownin FIGS. 9 a–9 d above and any modifications that would be apparent toone of ordinary skill in the art.

With reference to FIGS. 10 a–10 b, the desirability of using as long anarm as is possible is illustrated. FIG. 10 a shows the motion of an armhaving a length of 600 units as its non-pivoting end moves a distance of100 units vertically (y-direction). FIG. 10 b shows the motion of an armhaving a length of 300 units as its non-pivoting end moves a distance of100 units vertically (y direction). Because each arm pivots around asingle point, the second end moves in an arcuate manner. When the secondend is displaced 100 units vertically, the arm will sweep an angle of aparticular number of degrees, and the second end will be displacedhorizontally, due to the nature of rotational motion. When the longerarm is used, the angle swept is less (9.6° instead of 19.2°) and thehorizontal (x-direction displacement is also less (2.1 units instead of4.2 units). The reduced angular displacement and horizontal displacementare desirable, when considered in the context of the use of thetechnology in a suspension system. In the case of a suspension system, avertical displacement occurs when the track or wheels contact anobstacle, such as a log, rock, or other discontinuity of the land. Whenthe track contacts a log or other obstacle that is 100 units high, thetrack and axle must displace 100 units in order to pass over theobstacle. It is desirable that the track, wheels, and other suspensioncomponents (i.e., transverse suspension members 218 a, 218 b, 218 c) bemoved laterally the minimum possible distance, so that the direction ofthe track is not displaced. It is also desirable that the angulardisplacement of the arm be minimized, as a lower angular displacementrequires less of a clearance between the arm and other portions of thevehicle, such as frame components and the like, allowing greaterflexibility in designing the underbody of the vehicle generally.Accordingly, the extension of the transverse suspension members as greata distance as possible across the vehicle is desirable.

FIG. 11 is a partial cut away view of further modified suspension systemof the present invention. The illustrated suspension system includesseveral components that are identical to those previously describedherein with reference to FIGS. 6 and 8. Accordingly, several componentsthat have been described hereinbefore will not be described in detailhereinafter.

The illustrated suspension includes an A-arm 262, two transversesuspension members 218 b, 218 c, and two cushions 220 a, 220 b, each ofwhich are attached, either directly or indirectly, to both the beam 202and the frame (not shown) by means of a joint or series of joints thatpermit motion with three degrees of rotational freedom. The A-arm 262 isattached at a first point to the beam 202, and is attached to the frameat two spaced apart locations, as will be appreciated by those skilledin the art based upon the illustration of FIG. 11. In the most preferredembodiment, a ball joint-type joint is at least used to attach the A-arm262 to the beam 202. It will be apparent to a person of ordinary skillin the art that the connection with the frame will also permit rotationabout a primary axis of rotation, with some degree of freedom aboutother axes in order to be functional.

The A-arm 262 is attached to the beam 202 and the frame at an angle to ahorizontal plane. Preferably, this angle is between about 10–20° and,more preferably, this angle is approximately 16°. It is also mostpreferable that the A-arm 262 be attached to the top 224 of the beam 202at the forward end 202 a of the beam 202. The position and angle of theA-arm are important to force the mid axle 204 a at the forward end 202 aof the beam 202 to retract at a mechanical compliance angle of between5° and 15°. As noted hereinbefore, because the beam 202 is not securedby a true axle, the beam 202 tends to rotate about the rear hub 206 b,as it is the most secure. In an ordinary rotation, the mid axle 204would tend to move primarily upwardly, and then would move at an anglebackwardly. However, in order to have an appropriate ride, it isdesirable for the mid axle 204 to move more angularly at the mechanicalcompliance angle. The use of the angled A-arm 262 in the forwardposition provides a relatively stiff guidance system for the forward end202 a of the beam, causing the mid axle to move more rearwardly as itdeflects upwardly, due to encountering rocks, sticks, ruts, and otherthings that are likely to be encountered in an off-road environment.FIG. 14 shows a comparison of the motion of the mid axle 204 along avertical path V, a rotational path R, and the desirable mechanicalcompliance angle M (the angles being exaggerated due to spaceconstraints). The A-arm 262, because it is placed near to the forwardend 202 a of the beam 202, has the greatest ability to govern the motionof the beam. The A-arm 262 is preferably provided with a stop (notshown) that serves to prevent the beam 202 from rotating too greatlyfrom its general horizontal placement. Some of this function can also beperformed by one of the cushions 220 a, 220 b (the structure of which isdescribed in greater detail below). The A-arm 262 serves to transmitmotive and braking forces between the frame and the beam 202.

The transverse suspension members 218 define the camber and toe of thewheels 208 a, 208 b and the beam 202. Camber and toe are staticmeasurements that remain relatively constant regardless of the verticalor rotational position of the beam 202. FIG. 15 shows the generalmeaning of camber. The wheel 208 a is typically placed at a slight angleto the ground, to provide additional stability. The angle α between avertical position of the wheel V and the angle at which the wheel 208 ain fact rests, angle C, is known as the camber. Camber angle α ispreferably 0° but, in actual practice, is typically between about 0° andabout 5°. FIG. 16 shows the general meaning of toe. The beam 202 andwheels 208 a are angled slightly from the horizontal axis. The anglebetween the vertical direction (the direction of motion) H and the angleT at which the beam 202 rests is known as the toe angle β. The toe angleβ typically has a value between about 0° and about 2°. It is desirablethat the toe angle β be about 0° in the present application.

It is preferable that two cushions 220 a, 220 b be used in the presentembodiment. One of the cushions 220 a is preferably placed near thefront end 202 a of the beam 202. The other of the cushions 220 b ispreferably placed near the rear end 202 b of the beam 202. In thepreferred embodiment, the front cushion 220 a is attached to the A-arm262, rather than being directly connected to the beam 202. Thisplacement is to conserve the space used on the beam 202. However, thefront and rear cushions 220 a, 220 b can be placed in other locations,either directly or indirectly attached to the beam 202. The cushions 220a, 220 b primarily serve to enhance the ride of the vehicle, but mayalso serve as a stop to prevent over rotation of the beam 202.

A modified version of the structure is shown in FIG. 12. In FIG. 12, thebeam 202 is suspended by two transverse suspension members 218 a, 218 c,two cushions 220 a, 220 b, and an A-arm 262, each of which is preferablyjoined to at least one of the frame or the beam with a ball joint.Insofar as these members are structurally substantially the same as theparts with the same names described in connection with FIG. 11 above,they are not described in detail hereinafter. The primary differencebetween the embodiment of FIG. 11 and the embodiment of FIG. 12 is theplacement of the A-arm 262.

In the embodiment of FIG. 12, the A-arm 262 is attached to the beam 202on the bottom of the beam 202 and near the center of the beam 202. Asnoted above, the A-arm 262 is secured to the frame at an angle, which inthis case may be between about 5° and about 10°. Instead ofincorporating a stop into the A-arm 262, it is preferable to use amechanical stop 270, which may be a rubber bumper type stop on the frameto prevent the beam 202 from contacting the frame. While thisconfiguration will work satisfactorily under most conditions, it isconsidered to be less desirable than that of FIG. 11, as the placementof the A-arm 262 further from the forward end 202 a of the beam 202limits the force of the A-arm 360 to deflect the normal rotation of theA-arm 262. In addition, placement of the A-arm 262 on the bottom of thebeam 202 increases the risk of damage to the A-arm 262 due to contact ofthe A-arm 262 with the ground or other debris. Accordingly, thisconfiguration may be considered to be less desirable.

A modified version of the A-arm suspension assembly is shown in FIG. 13.In FIG. 13, the beam 202 is again held by two transverse suspensionmembers 218 a, 218 c, two cushions (not shown), and an A-arm 262, whichare preferably joined to at least one of the frame or the beam with aball joint. The primary difference between the embodiment of FIG. 11 andthat of FIG. 13 is the placement of the A-arm 262.

In the embodiment of FIG. 13, the A-arm is attached to the beam 262 onthe bottom of the beam 202 and near the rearward end 202 b of the beam202. As noted above, the A-arm 262 is secured to the frame at an angle.Instead of incorporating a stop into the A-arm 262, it is preferable touse a mechanical stop (not shown), which may be a rubber bumper typestop on the frame, to prevent the beam 202 from contacting the frame.This configuration is less desirable, as the placement of the A-arm 262further from the forward end 202 a of the beam 202 limits the force ofthe A-arm 262 to deflect the normal rotation of the A-arm 262. Inaddition, placement of the A-arm 262 on the bottom of the beam 202increases the risk of damage to the A-arm 262 due to contact of theA-arm 262 with the ground or other debris. Accordingly, may beconsidered to be relatively less desirable. Although the embodiments ofFIGS. 12 and 13 are less desirable than the embodiment of FIG. 11, theyare satisfactory configurations for many uses.

1. A half-track vehicle, comprising: (a) a frame having a first side anda second side; (b) a first beam; (c) a second beam; (d) a firstsuspension system suspending the first beam from the frame adjacent thefirst side of the frame; (e) a second suspension system substantiallyseparate from the first suspension system suspending the second beamfrom the frame adjacent the second side of the frame; (f) a forwardwheel and a rearward wheel attached to each beam; and, (g) wherein saidfirst suspension system includes at least one element that is attachedto one of said frame and said first beam in a manner that permits threedegrees of rotational movement and that transmits motive force from saidfirst beam to said frame; and (h) wherein said second suspension systemincludes at least one element that is attached to one of said frame andsaid second beam in a manner that permits three degrees of rotationalmovement and that transmits motive force from said second beam to saidframe.
 2. The half-track vehicle according to claim 1, wherein said atleast one element of each of said first and second suspension systemscomprises a trailing arm.
 3. The half-track vehicle according to claim2, wherein said trailing arm of each of said first and second suspensionsystems is secured to a forward end of the beam supported by thesuspension system adjacent said forward wheel and extends forwardlytherefrom to the frame.
 4. The half-track vehicle according to claim 3,wherein said trailing arm of each of said first and second suspensionsystems is secured to a top of the beam supported by the suspensionsystem.
 5. The half-track vehicle according to claim 4, wherein saidtrailing arm of each of said first and second suspension systems issecured to the beam supported by the suspension system such that saidforward wheel, upon engagement with an obstacle, retracts at amechanical compliance angle of between about 5–15°.
 6. The half-trackvehicle according to claim 5, further comprising a stop to limitrotation of the trailing arm of each of said first and second suspensionsystems.
 7. The half-track vehicle according to claim 2, furthercomprising a stabilizer bar extending between said first and secondbeams, said stabilizer bar serving to equalize pressures experienced bysaid first and second beams.
 8. The half-track vehicle according toclaim 7, wherein said trailing arm of each of said first and secondsuspension systems is secured to a forward end of the beam supported bythe suspension system adjacent said forward wheel and extends forwardlytherefrom to the frame.
 9. The half-track vehicle according to claim 8,wherein said trailing arm of each of said first and second suspensionsystems is secured to a top of the beam supported by the suspensionsystem.
 10. The half-track vehicle according to claim 9, wherein saidtrailing arm of each of said first and second suspension systems issecured to the beam supported by the suspension system such that saidforward wheel, upon engagement with an obstacle, retracts at amechanical compliance angle of between about 5–15°.
 11. The half-trackvehicle according to claim 10, further comprising a stop to limitrotation of the trailing arm of each of the first and second suspensionsystems.
 12. The half-track vehicle according to claim 2, wherein saidtrailing arm of each of said first and second suspension systems is anA-arm.
 13. The half-track vehicle according to claim 12, wherein saidA-arm of each of said first and second suspension systems is secured toa forward end of the beam supported by the suspension system adjacentsaid forward wheel.
 14. The half-track vehicle according to claim 13,wherein said A-arm of each of said first and second suspension systemsis secured to a top of the beam supported by the suspension system. 15.The half-track vehicle according to claim 14, wherein said A-arm of eachof said first and second suspension systems is secured to the beamsupported by the suspension system such that said forward wheel, uponengagement with an obstacle, retracts at a mechanical compliance angleof between about 5–15°.
 16. The half-track vehicle according to claim14, further comprising a stop to limit rotation of the A-arm of each ofsaid first and second suspension systems.
 17. The half-track vehicleaccording to claim 13, further comprising first and second cushions oneach of said first and second suspension systems, said first cushionbeing secured to the forward end of the beam supported by the suspensionsystem at a location in common with said A-arm, and said second cushionbeing secured to a rearward end of the beam supported by the suspensionsystem.
 18. The half-track vehicle according to claim 12, furthercomprising a stabilizer bar extending between said first and secondbeams, said stabilizer bar serving to equalize pressures experienced bysaid first and second beams.
 19. The half-track vehicle according toclaim 18, wherein said A-arm of each of said first and second suspensionsystems is secured to a forward end of the beam supported by thesuspension system adjacent said forward wheel and extends forwardlytherefrom to the frame.
 20. The half-track vehicle according to claim19, wherein said A-arm of each of said first and second suspensionsystems is secured to a top of the beam supported by the suspensionsystem.
 21. The half-track vehicle according to claim 20, wherein saidA-arm of each of said first and second suspension systems is secured tothe beam supported by the suspension system such that said forwardwheel, upon engagement with an obstacle, retracts at a mechanicalcompliance angle of between about 5–15°.
 22. The half-track vehicleaccording to claim 21, further comprising a stop to limit rotation ofthe A-arm of each of said first and second suspension systems.
 23. Thehalf-track vehicle according to claim 18, further comprising first andsecond cushions, on each of said first and second suspension systems,said first cushion being secured to the forward end of the beamsupported by the suspension system at a location in common with saidA-arm, and said second cushion being secured to a rearward end of thebeam supported by the suspension system.
 24. The half-track vehicleaccording to claim 23, wherein said vehicle defines a longitudinalcenterline and each suspension system includes a plurality of transversesuspension members, said transverse suspension members extending fromeach of said beams toward the other of said beams at least to saidlongitudinal centerline.
 25. A half-track vehicle defining alongitudinal centerline and having a first side and an opposite secondside, said vehicle comprising: (a) a frame; (b) a support structure thatis a bracket extending downwardly from the frame at the longitudinalcenterline; (c) a first beam disposed on said first side of saidvehicle; (d) a second beam disposed on said second side of said vehicle;(e) a first suspension system suspending the first beam from the frame;(f) a second suspension system suspending the second beam from theframe, said second suspension system being substantially separate fromthe first suspension system; (g) a forward wheel and a rearward wheelsecured to each of said first and second beams; (h) wherein said firstsuspension system includes at least one transverse suspension member,said at least one transverse suspension member extending from the firstbeam suspended by said first suspension system to said support structureat the longitudinal centerline; and (i) wherein said second suspensionsystem includes at least one transverse suspension member, said at leastone transverse suspension member extending from the second beamsuspended by said second suspension system to said support structure atthe longitudinal centerline.
 26. The half-track vehicle according toclaim 25, wherein a first transverse suspension member has a proximalend attached to said first beam and a distal end secured to said supportstructure, and wherein a second transverse suspension member has aproximal end attached to said second beam and a distal end secured tosaid support structure.
 27. The half-track vehicle according to claim26, wherein said distal ends of said first and second transversesuspension members define tubular housings that are rotatably secured tothe support structure.
 28. The half-track vehicle according to claim 27,wherein said tubular housings define passageways that are aligned withone another.
 29. A half-track vehicle defining a longitudinal centerlineand having a first side and an opposite second side, said vehiclecomprising: (a) a frame, said frame including a support structureintersecting said longitudinal centerline; (b) a first beam disposed onsaid first side of said vehicle; (c) a second beam disposed on saidsecond side of said vehicle; (d) a first suspension system suspendingthe first beam from the frame; (e) a second suspension system suspendingthe second beam from the frame, said second suspension system beingsubstantially separate from the first suspension system; (f) a forwardwheel and a rearward wheel secured to each of said first and secondbeams; (g) wherein said first suspension system includes at least onetransverse suspension member, said at least one transverse suspensionmember extending from the first beam suspended by said first suspensionsystem to said support structure; (h) wherein said second suspensionsystem includes at least one transverse suspension member, said at leastone transverse suspension member extending from the second beamsuspended by said second suspension system to said support structure;and (i) wherein said at least one transverse suspension member isattached to one of said frame and the beam suspended by the suspensionsystem in which the transverse suspension member is included in a mannerthat permits three degrees of rotational movement.
 30. A half-trackvehicle defining a longitudinal centerline and having a first side andan opposite second side, said vehicle comprising: (a) a frame, saidframe including a support structure intersecting said longitudinalcenterline; (b) a first beam disposed on said first side of saidvehicle; (c) a second beam disposed on said second side of said vehicle;(d) a first suspension system suspending the first beam from the frame;(e) a second suspension system suspending the second beam from theframe, said second suspension system being substantially separate fromthe first suspension system; (f) a forward wheel and a rearward wheelsecured to each of said first and second beams; (g) wherein said firstsuspension system includes at least one transverse suspension member,said at least one transverse suspension member extending from the firstbeam suspended by said first suspension system to said supportstructure; (h) wherein said second suspension system includes at leastone transverse suspension member, said at least one transversesuspension member extending from the second beam suspended by saidsecond suspension system to said support structure; and (i) wherein saidframe includes a first frame member disposed on said first side of saidvehicle and a second frame member disposed on a second side of saidvehicle, a first transverse suspension member has a proximal endattached to said first beam and a distal end secured to said secondframe member, and a second transverse suspension member has a proximalend attached to said second beam and a distal end secured to said firstframe member.